1. Field of the Invention
Exemplary embodiments of the present invention relate to an X-ray photographing apparatus, and more particularly, to a high voltage driving circuit for X-ray tube, in which a first voltage multiplying rectifier unit and a second voltage multiplying rectifier unit are in series connected to each other based on a high voltage generation unit to stably convert a high voltage power generated from the high voltage generation unit into a drive power for an X-ray tube with high energy efficiency, and in which a plurality of isolation transformers or high voltage transformers is in series connected to each other in the high voltage generation unit to divide a voltage of the second voltage multiplying rectifier unit into a withstanding voltage of the isolation transformers or the high voltage transformers, thereby ensuring excellent insulation properties.
2. Description of Related Art
An industrial X-ray photographing apparatus is an apparatus in which an generated X-ray beam is transmitted to a welded portion of an iron sheet or a concrete structure to capture an X-ray image of the welded portion or the structure so that a user can check whether or not the welded portion or the structure is in an abnormal state based on the captured X-ray image.
A high voltage driving circuit for X-ray tube used in a conventional industrial X-ray photographing apparatus will be described hereinafter in further detail with reference to FIG. 1.
The high voltage driving circuit for X-ray tube includes an inverter unit 10 for receiving a supply of a commercial AC power and generating a high-frequency AC power, a high voltage generation unit 20 for receiving a supply of the high-frequency AC power generated from the inverter unit 10 through a primary coil thereof and inducing a high-voltage power corresponding to the turns ratio of the primary coil and a secondary coil thereof to the secondary coil, a voltage multiplying rectifier unit 30 for receiving a supply of the high-voltage power from the high voltage generation unit 20 and generating a rectified high-voltage power having a level needed to drive the X-ray tube 40
In this case, the voltage multiplying rectifier unit increments the high-voltage power applied thereto from the high voltage generation unit 20 by a multiple of the applied high-voltage power to generate the rectified high-voltage power.
The X-ray tube 40 includes an X-ray tube housing 41 that is internally maintained in a vacuum state, a cathode 43 and an anode 45 that are disposed so as to be opposed to each other within the X-ray tube housing 41, and an cathode filament 47 connected at one end thereof to the cathode 43 so as to be opposed to the anode 45 within the X-ray tube housing 41. In this case, the anode 45 is grounded. The voltage multiplying rectifier unit 30 supplies the rectified high-voltage power generated therefrom to the cathode 43 and the cathode filament 47 connected at one end thereof to the cathode 43, and the filament driving power supply unit 50 supplies a drive power to the cathode filament 47.
A filament current generated by the drive power supplied to the cathode filament 47 heats the cathode filament 47 to generate thermal electrons, which in turn collide with the anode 45 by a voltage difference between the anode 45 and the cathode filament 47 to generate an X-ray beam.
FIG. 2 is a circuit diagram illustrating a voltage multiplying rectifier unit of a conventional high voltage driving circuit for X-ray tube.
Referring to FIG. 2, when a high frequency power (NP) is applied to the primary coil of the high voltage generation unit 20, the high voltage generation unit 20 increases a level of the high frequency power (NP) to a level corresponding to the turns ratio of the primary coil and the secondary coil thereof to cause a high-voltage power (NS) to be induced to the secondary coil.
The voltage multiplying rectifier unit 30 includes a plurality of unit voltage multiplying circuits (30-1, 30-2, 30-3, . . . , 30-N), which are connected in series. Each time the high-voltage power (NS) sequentially flows through the respective unit voltage multiplying circuits (30-1, 30-2, 30-3, . . . , 30-N), the high-voltage power (NS) applied to each of the unit voltage multiplying circuits (30-1, 30-2, 30-3, . . . , 30-N) is rectified into a high-voltage power that is incremented by a multiple of the applied high-voltage power (NS) by the voltage multiplying rectifier unit 30, and then is outputted. The voltage multiplying rectifier unit 30 generates a rectified high-voltage power having a level enough to allow an X-ray beam to be generated from the X-ray tube 40 through the plurality of the unit voltage multiplying circuits (30-1, 30-2, 30-3, . . . , 30-N) that is cascaded.
However, in order to generate the rectified high-voltage power having a level enough to allow an X-ray beam to be generated from the X-ray tube 40, it is required that the voltage multiplying rectifier unit 30 should include a plurality of unit voltage multiplying circuits. In addition, the more the number of the unit voltage multiplying circuits, the lower the energy transfer efficiency and the higher the ripple voltage, which makes it difficult to include an infinitely increased number of the unit voltage multiplying circuits. Further, it is required that the more the number of the unit voltage multiplying circuits, the higher the capacity of the condenser and diode should be, which makes it impossible to manufacture the products following a trend toward thinness and lightness. Thus, there occurs a problem in that a high voltage driving circuit for an X-ray tube 40 cannot not be manufactured in an inexpensive and compact manner.